“There will be an investigation on what happened,” he said. “One of them has been rescued and the flight data recorder has been recovered. Analysis will be done on that,” he told AFP.

The helicopter was still missing, he said without elaborating. The rescued man was uninjured and the helicopter issued a distress signal immediately after it lost contact, according to national broadcaster NHK.

Japan’s military and coastguard are using a total of seven vessels and 10 aircraft to look for the missing men, the navy official said.